This invention relates to optical smoke detectors having simple and inexpensive test devices such as are described in greater detail in U.S. Pat. No. 3,868,184 and U.S. Pat. No. 4,166,698.
In both the above mentioned patents the optical smoke detectors comprise a beam of light directed from a light source along a path or axis usually located within a dark smoke chamber having ports to admit air but exclude ambient light. Light scattered from particles in the light path is viewed by a photocell which in turn responds by sending a signal to an associated alarm circuit. Accordingly, the introduction of a fine, fragile wire or a light scattering flag, from an unviewed position to a viewed or detection zone intruding position in the dark smoke chamber, is used to simulate smoke particles in the chamber.
Although the art of record is effective in extemporaneously testing the capacity of an optical smoke detector to alarm in response to a predetermined smoke density, such art requires the relatively strict maintenance of the integrity of a dark smoke chamber. In addition, the use of a fine, fragile wire or a light scattering flag sometimes still fails to provide a testing means that is completely independent of the position of the filament in the light source and of consequent variations in the location of the light path in the dark chamber.
It is therefore an object of the present invention to provide an optical smoke detector with testing means that need not include a fine, fragile wire or a light scattering flag and which is even more independent of filament position in different light sources and of the consequent variations in the direction of the light path in a dark chamber than the prior art.
It is a further object of the present invention to provide an optical smoke detector with testing means that are less dependent upon the absence of ambient light than the prior art.